Tool bits for insertion into a tool bit receptacle of manually operated tools comprise stop faces for torque transmittal effective in the circumferential direction, as well as stop faces effective in the axial direction, for axial retention of the tool bits in a tool bit receptacle of the manually operated tools. It is common to dispose the stop faces effective in circumferential direction at entrainment grooves which are open towards the free end of the clamping shank.
Tool bit receptacles provided for the above-mentioned tool bits, comprise a receiving area which usually is equipped with entrainment strips so that appropriate faces matching the stop faces on the tool bit are formed. It is common to provide axially closed grooves at the clamping shank of the tool bits with which matching faces in the tool bit receptacle cooperate which are mostly disposed at radially displaceable locking elements of the tool bit receptacle in order to provide axial retention. It is necessary to shift the locking elements radially out of the axially closed grooves of the tool bits for removing the tool bits out of the tool bit receptacle. Tool bits as well as a tool bit receptacle of this type are disclosed, for instance, in DE-PS 2,551,125.
While the stop faces of the tool bit effective in the axial direction need not meet any particularly large requirements, since they are used only for retaining the tool bits in the tool bit receptacle, the stop faces, effective in the circumferential direction, have to meet stringent demands because of high torque transmittal. Because of these high torques to be transmitted, a corresponding large dimensioning of the stop faces, effective in the circumferential direction is required. Since the dimensional sizing of the clamping shank is limited, the dimensioning of the stop face effective in the circumferential direction is also limited, especially if one has to meet dimensional requirements involving cross-sectional weakening of the clamping shank. All these limiting values in dimensioning of the stop faces effective in the circumferential direction lead to considerable wear of the stop faces effective in the circumferential direction, resulting in a premature failure of the tool bits because of the torques which must be transmitted, especially with tool bits functioning with larger diameters of the cutting area.
DE-OS 38 43 465 discloses a tool bit having projections upstream of the stop faces in the direction of the working area which radially exceed the diameter of the clamping shank. These projections form radially extending entrainment faces. The tool bit chuck or tool bit receptacle, also disclosed in this publication, comprises recesses for the projections so that appropriate matching faces are formed for the entrainment faces.
The projections known from the above publications are configured in such a way that the entrainment faces protrude radially directly from the diameter of the clamping shank and have an extraordinary small radial dimension, compared to their longitudinal extent. This dimensioning of the entrainment faces does not permit carriage of larger torques and thus effectively to unload the stop faces.
It is therefore an object of the present invention to provide a tool and tool holder for manually-operated tools in which the dimensioning of the entrainment faces permits the carriage of larger torques.
Another object of the invention is to provide a strong and efficient tool and tool holder for manually operated tools.